Related links:

Eris - a dwarf planet

Eris is a dwarf planet in our Solar System. Eris was one of the first three objects classified as a dwarf planet, along with Pluto and Ceres. Eris was first spotted in January 2005.

Eris is a large sphere of ice and rock
similar to Pluto. It orbits the Sun on the
edge of the Solar
System. The diameter of Eris is about 2,500 km (1,553 miles). We aren't sure of its exact size because it is so far away and very
hard to see, even with the world's biggest telescopes. If it really is 2,500 km across then it is a little larger than Pluto, which has a diameter of 2,390 km (1,490 miles).

Some astronomers called Eris our
Solar System's "tenth planet" when it was first discovered. After a lot of discussion, astronomers decided to make up a new category for objects like Eris. That is where the idea of dwarf planets came from.

Eris was discovered by Michael Brown, Chad Trujillo, and David Rabinowitz. When it was first discovered, it was given the temporary name "2003 UB313". Astronomers also called it by the nickname "Xena", after the main character in the TV show "Xena: Warrior Princess".

Eris has a moon named Dysnomia. Before the moon's official name was announced, the moon had a nickname too. It was called "Gabrielle", the name of another character from the TV show.

The orbit of Eris is odd. The orbit is not
a circle, so Eris moves closer
to and
further
from the Sun as it goes around. It takes Eris 557 years to go around one
time! The orbit of Eris is also tilted... it doesn't move in the same plane that
the other planets orbit in.

You might also be interested in:

In 2006 the International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System. Their scheme includes three classes of objects: "small solar...more

Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more

The outer edge of our Solar System is not empty. There are many huge spheres of rock and ice out near Pluto's orbit and beyond. Astronomers have a name for everything further out than the planet Neptune....more

Do you know what a planet is? If so, you are doing better than professional astronomers! Right now astronomers aren't quite sure how to define a planet. Maybe you've heard that some astronomers think Pluto...more

You may think that most objects in space that orbit something else move in circles, but that isn't the case. Although some objects follow circular orbits, most orbits are shaped more like "stretched...more

Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more